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Abstract It is the major biochemical transducer that converts the potential (chemical) energy into kinetic (mechanical) energy. It is a pulling, not a pushing machine, therefore, a given muscle must be antagonized by another group of muscles or another force such as gravity or elastic control (Murray et al., 1996). Structurally, there are three types of muscles : skeletal muscle, smooth muscle, and cardiac muscle (Harold, 1986). The muscle is one of the components of the motor unit which consists in addition of : the motor neuron and its axon, the peripheral nerve and the neuromuscular junction. Myopathy is a muscle disease not related to a demonstrable alteration in the innervation of muscle (Mastaglia and Walton, 1990). The Primary Myopathies Include: A- Muscle Dystrophies : The term dystrophy coined by Erb 111 1891 means abnormal growth and is derived from the Greek trophe meaning nourishment. Muscle dystrophy is distinguished by four obligatory criteria: - It is a primary myopathy. - There is a genetic basis for the disorder. - The course is progressive. - Degeneration and death of muscle fibers occur at some stage in the disease (Dubowitz, 1989). B- Congenital Myopathies: They are characterized by: 1- Relatively non progressive course. 2- Muscle weakness is present at birth or appears in the early childhood. 3- The muscle bulk is normal or reduced, there is no muscle hypertrophy. 4- Skeletal abnormalities are common (Banker, 1986). C- Mitochondrial Myopathies: Certain genetic abnormalities of mitochondrial ongm cause identifiable myopathic syndromes. |